Tuning device for radio apparatus



Nov. 3, 1931. D. R. DE TAR TUNING DEVICE FOP. RADIO APPARATUS Filed June 6, 19.27

m/entor' Donald RDeTar,

Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE DONALD R. DE TAR, OF SGHENECTADY, NEW YORK, ASSIGN OR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK TUNING DEVICE FOR RADIO APPARATUS Application led June 8, 1927. Serial No. 196,742.

My invention relates to tuning devices for radio apparatus, and has for its principal object the provision of an improved tuning device that will operate smoothly 5 without slippage or backlash.

In the operation of radio receiving apparatus, it is desirable that the variable condenser or other tuning device of the apparatus be driven through some form of speedreducing mechanism in order that a condition of exact resonance with any given broadcasting station may be readil produced. Various forms of gear and rictionk drives have been provided for this purpose in the past, but these drives have not been altogether satisfactory for the reason that the gear drives do not operate without'backlash and the friction drives are likely to slip, especially after being used for sometime.

In accordance with my invention these difficulties are avoided by means of a tuning device provided with a drive mechanism which comprises a flexible member positively attached to the movable member of the device and arranged to be maintained substantially taut under all conditions of operation.

My invention will be better understood from the following description when considered in connection with the accompanying 3o drawings and its scope will be pointed out in the appended claims.

Referring to the drawings Fig. 1 illustrates a tuning device wherein my invention has been embodiedand Fig. 2 shows certain details of the device illustrated by F ig. 1,

This device comprises a plurality of variable condensers each provided with a rotor 1 mounted on a shaft 2 and with astator 3 mounted in a tub-shaped support 4. Adjustment of the different condensers is effected by a drive mechanism comprising a pulley 5 mounted on the shaft 2 and provided with grooves adapted to receive a small metal cable 8 through which it is coupled to a pair of grooved drums 6 and 7. The drums 6 and 7 areA mounted on a shaft 9 which is arranged to be rotated by a knob l0 in bean ings formed by a member I11 attached to the support 4. In order to maintain the length of cable between the drums 6 and 7 substantially constant for all adjustments of the rotors 1, the drums 6 and 7 are .so arranged with respect to the pulley 5 that the cable at opposite sides of the pulley 5 makes equal angles with the vertical axis of the shaft 2 when the points of tangency between the drums and cable are in the middle of their travel. As illustrated, these points of tangency move in the same direction along the axes of the drums.

Between the grooved drums 6 and 7, the cable 8 passes along a groove near the left hand edge of the pulley, through a notch 12 to the inner periphery of the pulle through a notch 13 to a groove near the riglyit hand edge of the pulley, under a tightening lug 14 and further along a groove near the right hand edge of the pulley to the drum 7. It will be apparent that the connection of the cable between the grooves 12 and 13 have the effect of anchoring it to the pulley 5 so that it can not slip in the grooves. Under these conditions, the tension of the cable 8 is dependent on the adjustment of a screw 15 which holds the lug 14 in contact with the cable, and slippage of the cable in the grooves of the drumis prevented.. Between the grooves on the drum 5 is supported an outer cylindrical member 16 to which a log-sheet 17 may be attached by means of screws 18 and 19 for the purpose of loggingthe tuning kposition for different stations. The weight of the rotors 1 is counterbalanced by a counterweight 20 and a stop 21 is arranged to cooperate with stops on the left hand side of the pulley 5 for the purpose of limiting the rotation of the shaft 2. It will of course be understood that all of the tuning device except the knob 10 may be mounted within a casing and that an opening may be provizded in the casing for reading the log sheet 1 Assuming the various parts of the tuning device to be in their illustrated positions, rotation of the knob 10 in a clockwise direction causesthe cable 8 to wind from the drum G onto the drum 7, thus rotating the pulley 5 and the shaft 8 in a clockwise direction. Ro tation of the knob 10 in a countercloclm'ise direction causes the cable to wind from the drum 7 onto the drum 6 and produces counattached to said pulley and enga 'ng the caterclockwise rotation of the shaft 2. As preble intermediate its ends for aihsting the viously-indicated, the vcable 8 is preferably tension of said cable throughout its length.

W Y ,Y so arranged that its points of tangency move In witness whereof, I have hereunto set my along the drums 6 and 7 in the same direchand this 3d day of June, 1927. 7o

tion and variation inthe length of cable be- DONALD R. DE TAR. tween the drums is avoided by so arranging the drums with respect to the pulley that the points of tangency between the cable and 10 drums move through equal distances with 75 respect to the vertical axis of the shaft 2 as v the knob 10 is rotated. It has been found that with these precautions the tautness of the cable is substantially. constant throu h .y

" l5 the operating range of the device and t e so l 'condensers are ad'usted from one position to y another without slippage or backlash.

What I, claim as new and desire to secure by Letters Patent of the United States is: .2Q 1. In a radio ap aratus, thevcembination of a pulley provided) with peripheral grooves near its opposite edges, a tunmg devlce mechanically fixed to said ulley, rotatable drum means, a single ilexi 1e cord member 2? arranged to lie in and be anchored between 90 said'grooves and arranged to be simultane-` ousl wound on and unwound from said ro- 5 tata le drum means, an outer cylindrical member attached. to the periphery of said 3 pulley, and means for attaching a log sheet u to said cylindrical member. I l2. In a radio ap aratus,.the combination of a pulley provide with peripheral grooves near its opposite edges, a tuning device comv 35 rising a rotor mechanically-fixed to said pul- 100 ey, rotatable drum means, a single exible cord member arran ed to lie in and be anchored between sai grooves and arranged to be simultaneously wound on and unwound v o from said rotatable drum means, an'outer 105 cylindrical member attached to saidpulley concentrically therewith, and means attached to said pulley and mounted in the space between said pulley and the outer cylindric'al 45. member for counterbalancing the weight of no said rotor. l

3. A radio apparatus including a condensf er rotor mounted on a rotatable shaft, a pnl.-

,ley provided with peripheral grooves near itsv v r QQ opposite edges, a pair of rotatable drums, a n

" single flexible cable4 arranged to lie in and f extend between said grooves and to be simul` taneousl wound upon one of said drums and unwoun from the 'other of said drums, and

55. a single stop arran ed to limit the rotatio of said` pulley in eit er direction. v f:

4. A radio apparatus including a condenser rotor mounte on a rotatable shaft, a pulley provided with peripheral grooves near A 90.- its op osite edges, a pair of rotatable drums, a sing e flexible cable arranged to liev in and extend between said grooves and to be simultaneously wound upon one of said drums and unwoun from the other of said drums, and

`.6.5 adjustable means including a movable lug '130 

